Solar cell modules are devices that convert light energy from the sun into electrical energy, and are attracting attention as systems capable of generating electrical power without discharging carbon dioxide.
FIG. 3 is a schematic cross-sectional view of an example of a solar cell module.
This solar cell module 100 is roughly composed of solar cells 101 composed of crystalline silicon, a sealing material 102 that seals the solar cells 101, a front protective sheet (front sheet) 103 laminated onto the sealing material 102, and a back protective sheet (back sheet) 104 laminated into the sealing material 102.
In order to impart weather resistance and durability to the solar cell module 100 enabling it to withstand outdoor and indoor use over a long period of time, it is necessary to protect the solar cells 101 and the sealing material 102 from wind and rain, humidity, dust and mechanical impacts while also maintaining the inside of the solar cell module 100 in a sealed state that is isolated from the outside air. Consequently, the front protective sheet 103 and the back protective sheet 104 are required to have superior weather resistance, and are required to have a low level of water vapor permeability in particular.
A water impermeable sheet has been disclosed in which a vapor deposited layer that is substantially impermeable to water is provided on a base sheet composed of a resin such as polyethylene terephthalate for use as a protective sheet for a solar cell module having low water vapor permeability (see, for example, Patent Document 1).